The present invention relates to a bearing apparatus for a wheel for supporting a wheel of an automobile, and more particularly to a bearing apparatus for a wheel of a type that a hub, an outer joint member of a constant velocity universal joint and double rows of wheel bearings are united and at least one of the double rows of inner raceways is integrally formed in the outer joint member, or of a type that one of the inner raceways is directly formed in the hub and another of the inner raceways is formed in an inner race fitted to the hub.
Driving wheels of the automobile such as rear wheels of an FR vehicle, front wheels of an FF vehicle and all wheels of a 4WD vehicle are supported to a suspension apparatus by a bearing apparatus for wheels. The bearing apparatus mentioned above is structured, as shown in FIG. 43, such that a hub 10, a bearing 20 and a constant velocity universal joint 30 are united, one inner raceway 12 of double rows of inner raceways is formed in the hub 10, and another inner raceway 42 is formed in an outer joint member 40 of the constant velocity universal joint 30.
The hub 10 has a flange 14 for supporting the wheel, and the inner raceway 12 is formed on an outer peripheral surface close to the flange 14. The outer joint member 40 of the constant velocity universal joint 30 is constituted by a bowl-shaped mouth portion 43 and a solid stem portion 45, and is serration fitted to the hub 10 at the stem portion 45 and a shoulder surface 44 thereof is brought into contact with an end surface of the hub 10. The inner raceway 42 is formed on an outer peripheral surface close to the stem portion 45 in the mouth portion 43 of the outer joint member 40. Double rows of outer raceways 22 opposing to the inner raceways 12, 42 are formed on an inner peripheral surface of an outer member 21 (hereinafter, refer to as an outer race) of the bearing 20. Rolling elements 29 are assembled between the inner raceways 12, 42 and the outer raceways 22.
As shown by a reference numeral 45xe2x80x2, an axial end of the stem portion 45 protruding from the hub 10 is caulked, thereby connecting between the hub 10 and the stem portion 45, and the outer race 21 is fixed to the suspension apparatus by a flange 24 formed on the outer peripheral surface of the outer race 21, whereby the wheel is fixed to the flange 14 of the hub 10.
In the bearing apparatus mentioned above, a torque from an engine is transmitted to the hub 10 via the constant velocity universal joint 30 so as to rotate the wheel. Accordingly, it is necessary that the outer joint member 40 and the hub 10 are connected at a high reliability. However, since a great moment load is applied to the bearing portion particularly when the automobile turns, there is a disadvantage that the caulked portion is loosened in the case of caulking the axial end of the stem portion 45 of the outer joint member 40.
The bearing apparatus mentioned above is that one inner raceway 42 of the double rows of inner raceways 12, 42 is integrally formed with the outer joint member 40, however, as a bearing apparatus having another construction, there is a bearing apparatus structured such that one inner raceway is directly formed in the hub and another inner raceway is formed in an inner race fitted to the hub as an independent element from the hub.
FIGS. 44A and 44B show a representative embodiment of the bearing apparatus, in which FIG. 44A shows the bearing apparatus for a driving wheel and FIG. 44B shows the bearing apparatus for a driven wheel. Since a basic structure is common between the bearing apparatus for the driving wheel and the bearing apparatus for the driven wheel, a brief description will be given of a construction of the bearing apparatus for the driven wheel in accordance with FIG. 44A. The bearing apparatus is structured such that the hub 10, an inner race 80, the outer race 21, the double rows of rolling elements 29 and the constant velocity universal joint 30 are united. One inner raceway 12 of the double rows of inner raceways 12, 42 is directly formed in the hub 10 and another inner raceway 42 is formed in the inner race 80 fitted to the hub 10 as an independent element from the hub 10.
The hub 10 is structured such that the inner raceway 12 is formed in the outer peripheral portion and the flange 14 for supporting the wheel is formed in the end portion close to an outboard side. In this case, a side close to an outer side of the vehicle in a state of being assembled in the vehicle is called as an outboard side (a left side in the drawing) and a side close to a center portion of the vehicle is called as an inboard side (a right side in the drawing). A small diameter step portion 59 having a reduced outer size is formed in the inboard side end portion of the hub 10, and the inner race 80 independent from the hub 10 and having the inner raceway 42 formed on the outer peripheral surface is fitted to the small diameter step portion 59. Double rows of outer raceways 22 opposing to the inner raceways 12, 42 are formed on the inner peripheral surface of the outer race 21. The rolling elements 29 are interposed to be freely rotatable between the inner raceways 12, 42 and the outer raceways 22.
The outer race 21 is fixed to the suspension apparatus by the flange 24 (in FIG. 44, only a part thereof appears) formed on the outer peripheral surface of the outer race 21, whereby the wheel is fixed to the flange 14 of the hub 10. The stem portion 45 of the outer joint member 40 is serration fitted to a serration hole 63 of the hub 10, thereby transmitting a rotational drive force to the wheel fixed to the hub 10. A nut 69 is screwed to a male screw portion 67 at the front end portion of the stem portion 45, thereby connecting the bearing 20 and the constant velocity universal joint 30.
This kind of bearing apparatus is normally used by applying a pre-load to the bearing 20, and an accurate pre-load control is performed at a time of assembling. However, since the inner raceways 12, 42 are distributed to the hub 10 and the inner race 80, a change of a positional relation in an axial direction between the hub 10 and the inner race 80 results in a change of a size between the inner raceway 12 and the inner raceway 42, so that the bearing clearance changes and causes a pre-load omission. Accordingly, it is necessary that the hub 10 and the inner race 80 are connected to each other at a high reliability.
However, since a great moment load is applied to the bearing portion particularly when the automobile turns, there is a disadvantage that the caulked portion is loosened due to a spring back of the caulked portion or the other reasons in the case of caulking the axial end of the small diameter step portion 59 in the conventional hub 10. Further, the hub 10 and the inner race 80 has a relation pressure fitting with a interference, however, no specific device has been conventionally provided so as to prevent a relative rotation. Accordingly, when the relative rotation, that is, a creep is generated due to some reason, there is generated a problem that a damage is generated on the fitting surface between the hub 10 and the inner race 80, a seizure is generated and a interference is increased, whereby a service life is reduced.
A first object of the present invention is to prevent the hub and the constant velocity universal joint from being loosened. To achieve the foregoing object, the invention provides a bearing apparatus for a wheel which comprises a hub, a constant velocity universal joint and a bearing, these elements being united and at least one of double rows of inner raceways of the bearing being integrally formed with an outer joint member of the constant velocity universal joint, wherein the hub and the outer joint member are fitted to each other, and the fitted portion is at least partly expanded or contracted by caulking.
Embodiments for fitting between the hub and the outer joint member include a case of fitting a small diameter cylinder portion of the hub to a through hole of the outer joint member and a case of fitting a stem portion of the outer joint member in which at least an axial end portion is formed in a hollow cylindrical shape to a through hole of the hub.
The caulking operation by expanding the inner fitting member or contracting the outer fitting member can be performed by a hydroforming in addition to a press formation. For example, the caulking operation is performed by expanding the stem portion of the outer joint member to an outer diameter side from an inner diameter side. Otherwise, the caulking operation may be performed by contracting the hub to the inner diameter side from the outer diameter side.
The invention provides a bearing apparatus for a wheel wherein an uneven portion is formed in any one or both of the fitted surface of the hub and the fitted surface of the outer joint member.
As a result of the caulking operation due to the expansion of the inner fitting member or the contraction of the outer fitting member, the uneven portion on one fitted surface eats into another fitted surface so as to generate a plastic deformation, so that a firm connection can be achieved and a loosening can be prevented. As a concrete embodiment of the uneven portion, for example, there can be listed up a spiral shape such as a screw, a double-cut knurled shape, a serration or spline shape (hereinafter, the serration or spline is totally called as a serration) or the like.
The uneven portion mentioned above, a work hardening is generated due to an uneven formation, however, it is possible to further apply a hardening treatment to the uneven portion due to a heat treatment Accordingly, the uneven portion is hard to be crushed and firmly eats into the fitted surface in an opposite side, so that a firm plastic connection can be achieved.
The hub and the stem portion can be securely connected by welding both elements in the end portion in an axial direction of the fitted portion so that it is possible to more securely prevent the loosening. One or two or more welding points may be dispersed in a circumferential direction in addition to welding all the periphery.
The invention provides a bearing apparatus for a wheel wherein a taper angle that a diameter is increased in the axial end side is given to the fitted surface of the hub or the fitted surface of the outer joint member. Since the diameter of the axial end side of the fitted surface is increased, a come-out prevention operation can be achieved.
The invention provides a bearing apparatus for a wheel wherein a projection is provided on the fitted surface of the hub or the fitted surface of the outer joint member. For example, an annular projection continuously extending all around the periphery can be exemplified, however, the projection is not always to be continuously provided in a circumferential direction. Further, a spirally extending projection may be employed.
As an embodiment of forming the unevenness on both of the fitted surfaces, there can be exemplified a case that a serration hole of the hub and a serration shaft of the stem portion in the outer joint member are fitted. The invention provides a bearing apparatus for a wheel wherein a cross sectional shape of the fitted surfaces of the hub and the outer joint member fitted to each other is formed in a polygonal shape or a serration shape.
In the case of fitting the stem portion of the outer joint member to the through hole of the hub, the structure may be made such that a clip for come-out prevention is attached to an end portion of the stem portion protruding from the hub. Further, the structure may be made such that the axial end portion of the stem portion is caulked to the end surface of the hub so as to prevent coming out.
The invention provides a bearing apparatus for a wheel wherein a reinforcing member is pressure fitted into the through hole of the stem portion. Since a rigidity of the hollow stem portion, particularly of the caulked portion is increased, the loosening can be prevented. The reinforcing member may be formed in a cylindrical shape, a ring shape or a solid short shaft shape. In the case of a cylindrical shape with a bottom or a solid member, it is preferable to provide a small hole communicating with a bottom of the mouth portion. Otherwise, in order to compensate for a reduction of rigidity due to a hollow construction, a solid portion may be provided in a part of the stem portion, for example, an area close to the mouth portion. In this case, it is desirable to provided a ventilating small hole communicating with the bottom of the mouth.
It is possible to obtain an effect of radiating a heat generated by a heat generation of the inner race portion and a heat generation of the mouth portion of the constant velocity universal joint to the outside since the through hole communicating with the bottom of the mouth portion is provided in the stem portion so as to make the stem portion hollow. In this case, in order to prevent a grease charged into the mouth portion from leaking, an end plate is attached to the bottom of the mouth portion. It is desirable to provide a ventilating small hole in the end plate.
The invention provides a bearing apparatus for a wheel wherein a cooling fin member is attached within the stem portion. Since a radiating effect can be further improved by attaching the cooling fin member to the hollow portion, it is very useful for improving a durability of the bearing apparatus for the wheel.
The invention provides a bearing apparatus for a wheel wherein the hub and the outer joint member are serration fitted at an axial position which is different from the caulked portion to be expanded or contracted. In this case, a torque transmission between the hub and the outer joint member is performed by the serration portion and a come-out prevention is applied to the caulked portion.
The invention provides a bearing apparatus for a wheel wherein an area closer to the axial end side than the serration portion of the stem portion in the outer joint member is expanded by caulking. The hub and the outer joint member are fixed in an axial direction by the caulked portion and a come-out prevention is performed.
The invention provides a bearing apparatus for a wheel wherein the caulked portion is partly extended to the serration portion. The caulked portion can be utilized as a play insert for the serration by caulking so that the caulked portion is extended to the serration end portion in the hub side.
The invention provides a bearing apparatus for a wheel wherein the serration portion of the stem portion is expanded from an inner diameter side by caulking. Accordingly, any play in the serration portion is lost, and a loosening prevention effect can be further increased.
The invention provides a bearing apparatus for a wheel wherein a portion changing to the caulked portion from the serration portion of the stem portion is gradually expanded.
The invention provides a bearing apparatus for a wheel wherein a spacer ring is interposed between the fitted surfaces of the stem portion and the hub. It is possible to apply an unevenness formation on an outer peripheral surface of the stem portion, an inner peripheral surface of the spacer ring or both of these. Further, an unevenness formation may be applied to an outer peripheral surface of the spacer ring, an inner peripheral surface of the hub or both of these surfaces.
The invention provides a bearing apparatus for a wheel wherein an annular groove is provided on an inner peripheral surface of the hub and the swelled portion of the stem portion in the outer joint member is eaten into the annular groove. Since the swelled portion and the annular groove are engaged and a rigidity of the caulked portion becomes higher than that of a simple cylindrical shape due to the swelled portion, a more secure come-out prevention can be achieved.
A second object of the present invention is to prevent the hub and the inner race from being loosened. To achieve the foregoing object, the invention provides a bearing apparatus for a wheel which comprises an outer race having a flange for mounting to a vehicle body and double rows of outer raceways, a hub having an inner raceway opposing to one of the double rows of outer raceways of the outer race and a wheel mounting flange, an inner race having an inner raceway opposing to another of the double rows of outer raceways of the outer race and fitted to the hub, double rows of balls interposed between the outer raceways of the outer race and the inner raceways of the hub and the inner race, wherein an uneven portion is formed on any one of fitted surfaces of the hub and the inner race or both of them and both of the hub and the inner race are plastically connected by expanding the fitted portions or contracting the fitted portions. Since a connection strength can be increased due to the plastic connection in comparison with the conventional caulking operation, a problem that the hub and the inner race are loosened can be solved and a pre-load omission can be prevented.
Embodiments for fitting between the hub and the inner race include a case that the hub corresponds to an inner fitting member and the inner race corresponds to an outer fitting member and a case that the inner race corresponds to the inner fitting member and the hub corresponds to the outer fitting member.
In the case that a small diameter cylinder portion is formed in one end of the hub and the inner race is fitted to an outer peripheral surface of the small diameter cylinder portion, the uneven portion is formed on fitted surface of the inner fitting member, that is, the outer peripheral surface of the small diameter cylinder portion of the hub, the fitted surface of the outer fitting member, that is, the inner peripheral surface of the inner race or both thereof.
In the case that a small diameter cylinder portion is formed in one end of the inner race and the hub is fitted to an outer peripheral surface of the small diameter cylinder portion, the uneven portion is formed on fitted surface of the inner fitting member, that is, the outer peripheral surface of the small diameter cylinder portion of the inner race, the fitted surface of the outer fitting member, that is, the inner peripheral surface of the hub or both thereof.
As embodiments of the uneven portion formed on the fitted surface, there can be exemplified a spiral shape such as a screw, a double-cut knurled shape, a serration or the like. Then, the uneven portion on one fitted surface eats into another fitted surface by expanding or contracting the fitted portion, whereby the hub and the inner race are plastically connected. After fitting the hub and the inner race, the fitted portion of the inner fitting member is expanded or the fitted portion of the outer fitting member is contracted.
In the case of fitting the inner race to the outer peripheral surface of the small diameter cylinder portion of the hub, the fitted portion of the small diameter cylinder portion of the hub is expanded or the fitted portion of the inner race is contracted. In the case of fitting the hub to the outer peripheral surface of the small diameter cylinder portion of the inner race, the fitted portion of the small diameter portion of the inner race is expanded or the fitted portion of the hub is contracted.
The invention provides a bearing apparatus for a wheel, wherein the inner fitting member has an axial through hole. A through hole extending all along the axial length is provided in the hub when the hub is the inner fitting member, and a through hole extending all along the axial length is provided in the inner race when the inner race is the inner fitting member. According to the structure mentioned above, since the whole of the bearing apparatus has a hollow structure, a heat radiating effect can be increased and a durability can be improved by restricting an amount of temperature increase in the bearing portion.
The invention provides a bearing apparatus for a wheel, wherein hardening treatment by heat treatment is applied to the caulked portion between the hub and the inner race. The uneven portion has a higher hardness than the other portions due to a work hardening caused by the unevenness formation, however, since an elastic deformation after the caulking operation according to the expansion or the contraction is reduced by applying the hardening treatment by the heat treatment, it is possible to increase the loosening prevention effect.
The invention provides a bearing apparatus for a wheel, wherein the end portions of the fitted portions of the hub and the inner race are welded. Accordingly, it is possible to further securely connect the hub to the inner race. The structure may be made such that the welding operation is performed all around the periphery or one or two or more welding points are dispersed in a circumferential direction.
The invention provides a bearing apparatus for a wheel, wherein a clip is attached to the end portion of the inner fitting member so as to fix the hub to the inner race in an axial direction. When the hub is the inner fitting member, the clip is attached to an annular groove formed on the outer peripheral surface of the small diameter cylinder portion in the hub so as to be engaged with the end surface of the inner race, and when the inner race is the inner fitting member, the clip is attached to an annular groove formed on the outer peripheral surface of the small diameter cylinder portion in the inner race so as to be engaged with the end surface of the hub. Accordingly, it is possible to further securely connect the hub to the inner race.
The invention provides a bearing apparatus for a wheel, wherein a reinforcing member is pressure fitted into the caulked portion between the hub and the inner race. According to the reinforcing member, it is possible to increase a rigidity of the caulked portion to be expanded or contracted, and it is possible to prevent the caulked portion from being loosened due to a spring back of the caulked portion or the other reasons.
The invention provides a bearing apparatus for a driving wheel which comprises an outer member having a flange for mounting to a vehicle body and double rows of outer raceways, a hub having an inner raceway opposing to one of the double rows of outer raceways of the outer race and a wheel mounting flange, an inner race having an inner raceway opposing to another of the double rows of outer raceways of the outer race, an outer joint member of a constant velocity universal joint fitted to the hub and the inner race, double rows of balls interposed between the outer raceways of the outer race and the inner raceways of the hub and the inner race, wherein an uneven portion is formed on any one of fitted surfaces of the hub and the outer joint member or both of them and both of the hub and the outer joint member are plastically connected by expanding the fitted portions or contracting the fitted portions. It is possible to prevent the hub and the inner race from being loosened by expanding or contracting the fitted portions between the hub and the outer joint member so as to plastically connect both of them.
Further, a third object of the present invention is to prevent a creep of an inner race in a bearing apparatus for a wheel of caulking an end portion of a hub so as to fix an inner race. To achieve the foregoing object, the invention provides a bearing apparatus for a wheel which comprises an outer race having a flange for mounting to a vehicle body and double rows of outer raceways on an inner peripheral surface, a hub having a wheel mounting flange in an outboard side, structured such as to pressure fit an inner race into an inboard side, directly form an inner raceway in the outboard side of double rows of inner raceways opposing to the double rows of outer raceways of the outer race on an outer peripheral surface and form an inner raceway in an inboard side on the inner race, double rows of rolling elements interposed between the outer raceways of the outer race and the inner raceways of the hub and the inner race, the inboard side end portion of the hub being caulked to the outer diameter side so as to fix the inner race, wherein a preventing means for preventing a relative rotation by directly or indirectly engaging the hub with the inner race is, provided. The creep can be prevented and a durability can be improved by preventing the relative rotation between the hub and the inner race.
The invention provides a bearing apparatus for a wheel, wherein the preventing means for preventing the relative rotation between the hub and the inner race is a recess groove provided in an inner diameter of the end surface portion of the inner race. By providing the recess groove, the hub eats into the recess groove of the inner race when caulking the inner end portion of the hub, whereby a kind of key operation can be obtained. Accordingly, the hub and the inner race are locked in a rotational direction, whereby the creep can be prevented. The number of the recess groove is one or two or more, and when a multiplicity of recess grooves are arranged all around the periphery, they form a so-called serration.
The invention provides a bearing apparatus for a wheel, wherein the preventing means for preventing the relative rotation between the hub and the inner race is a recess portion formed in the end surface portion of the inner race and having a peripheral wall in which a distance from an axial core of the inner race is not uniform in a circumferential direction. In this case, when caulking the inner end portion of the hub, the hub is expanded along the recess portion. Since in the peripheral wall of the recess portion, the distance from the axial core of the inner race is not uniform, the hub and the inner race are locked in the rotational direction, whereby it is possible to prevent the creep. Exemplifying a concrete shape of the recess portion having the peripheral wall in which the distance from the axial core of the inner race is not uniform in the circumferential direction, there are a structure in which a contour of the peripheral wall is an oval shape, and a structure in which a contour of the peripheral wall is a complete round eccentrically formed with the axial core of the inner race. The peripheral wall may be parallel to an axis of the inner race or may extend in a direction crossing to the axis of the inner race such as a so-called bevel.
The invention provides a bearing apparatus for a wheel, wherein the preventing means for preventing the relative rotation between the hub and the inner race includes a spacer interposed between the caulked portion of the hub and the inner race, and the spacer is engaged with both of the hub and the inner race. The invention provides a bearing apparatus for a wheel, wherein the spacer is formed in an annular shape, and has a flat surface engaging with a flat surface formed in the outer peripheral portion of the hub in an inner peripheral portion thereof and a flat surface engaging with a flat surface formed in the outer peripheral portion of the inner race in an outer peripheral portion thereof. Accordingly, it is possible to prevent the both from relatively rotating by indirectly engaging the hub with the inner race, whereby it is useful for preventing the creep of the inner race.
This invention can be applied to both of the bearing apparatuses for the driven wheel and the driving wheel. Then, in the bearing apparatus for the driven wheel, the hub is not connected to the drive shaft whichever the hub is a solid one or a hollow one. On the contrary, in the bearing apparatus for the driving wheel, the outer joint member of the constant velocity universal joint is connected to the hub. Further, the structure can be made such that the outer joint member is connected to the serration hole of the hub by a serration formed in the stem portion thereof, the hub and the outer joint member are fixed to each other by fastening a nut to a screw formed in the stem portion.
The invention provides a bearing apparatus for a wheel, wherein an annular recess portion for receiving a caulked end portion of the hub is formed in an inner diameter side of a shoulder surface of the outer joint member of the constant velocity universal joint. Accordingly, since the annular shoulder surface in the outer diameter side of the recess portion is brought into contact with the side surface of the inner race without being interfered with the caulked end portion of the hub and an axial positioning of the inner race is performed, there is no fear that a bearing clearance is changed and a pre-load is omitted.
The invention provides a bearing apparatus for a wheel, wherein an inner end of a thin cylinder portion formed in an inboard side end portion of the hub is set to be closer to the axial end side than a crossing point between a load application line of the inboard side rolling element and an inner diameter surface of the inner race. Accordingly, since the thin caulked portion is disposed at a position shunting from the load application line, it is useful for maintaining a desired rigidity and preventing a creep of the inner race. In this case, in the bearing apparatus for the wheel shown in FIG. 44, a thin cylinder portion 61xe2x80x2 having a depth h is provided in an inboard side end portion of the hub 10 in order to facilitate the caulking operation, in this case, the thin cylinder portion 61xe2x80x2 partly extend to a fitted area between the thin cylinder portion 61xe2x80x2 and the inner race 80. In the wheel bearing of the automobile, a great moment load is applied to the bearing portion due to a swirling motion or the like, however, in particular, since the thin cylinder portion 61xe2x80x2 is provided in the inboard side, there is left a problem of a creep of the inner race 80 due to an insufficiency of rigidity as a problem to be solved.